Professional cameras are loaded with rolled sensitized film by placing a fresh roll of spooled film in the camera unwind section and pulling the backing paper across the exposure area and inserting the backing paper leader in the slot of the take-up spool and initiating wind-up. It has been estimated that 80% of the professional photographers automatically place their thumb on the take-up spool while partially advancing the spool to eliminate any problem with the leader not remaining in the spool slot (cinching). Though widely practiced, this is considered an unacceptable accommodation on the part of the customer. The remaining 20% of professional photographers do not attempt to accommodate this shortcoming of the backing paper leader and simply insert the leader in the slot and begin to wind. The result is that frequently the leader pulls free of the take-up spool (does not cinch) and the operation must be repeated until successful. This frequency of first time loading failures is unacceptable product performance that requires modifications be found to eliminate the need for either photographer accommodation or repeated attempts to successfully load a roll of professional film.
EP 0 763 768 A2 addresses the cinching problem by punching a hole in the polymer coated backing paper leader tab and modifying the take-up spool design to include a cinch post or pin which protrudes perpendicularly into the spool slot. This cinch post extends through the hole in the polymer coated backing paper leader when properly inserted to grip the backing paper leader as wind-up is initiated. This approach, though successful, suffers from two limitations in that it requires an expensive retooling to manufacture replacement take-up spools with the cinch post and the leader is difficult to remove for recycling after exposure of the film.
U.S. Pat. No. 1,441,146 addressed the cinching problem by utilizing a single-layer backing paper with sufficient stiffness to resist unfolding in the take-up spool slot and releasing during initiation of wind-up. However, the use of polymer coated backing paper has many positive attributes not easily obtainable with paper alone including reduced dirt from finishing operations, reduced self-abrasion, and fewer pinholes for better light protection. Therefore, although the single-layer backing paper structure addresses the cinching problem, it lacks the additional desired roll film backing paper characteristics of polymer coated backing paper.